Refining process



July 26, 1938. s. P. MILLER 2,124,860

' REFINING PROCESS Filed March '11, 1936 INVENTOl Patented July26, 1938Q UNITED STATES PATENT 1 OFFICE anrmme PROCESS Application March 11,1936, Serial No. 68,229

4 Claims.

This invention relates to the refining-of metals, and more particularly,to the melting and refining of non-ferrous metals in a cupola furnace.

This invention is in the nature of an improvement on the invention ofthe Cushion Reissue Patent No. 17,347, 'of July 2, 1929. That patentdiscloses a method of refining non-ferrous metals in a cupola furnaceinvolving the placing of a charge of non-ferrous metal on a bed ofpitchcoke and burning the coke in contact with the metal to supply theheat necessary to melt the metal. As pointed out in this patent, pitchcoke is substantially free of ash, sulphur and othermaterials having adeleterious .efiect upon the non-ferrous metals refined in the cupola.Hence, by following the practice of this patent, the nonferrous metalswithdrawn from the cupola are not contaminated by impurities containedin the fuel employed in the cupola but are in a refined state of highquality and do not require a subsequent refining operation.

By the term non-ferrous metal as used in the specification and claimsherein areme'ant those metals other than ferrous metalswhich can bepractically melted ina cupola furnace and this term is intended toinclude the metals lead, copper, nickel, aluminum, tin, antimony,zinc,'and alloys thereof but to exclude easily oxidizable metals such asmagnesium, and alkali and alkali earth metals.

It is an object of this invention to provide a process for meltingandrefining metals, and particularly non-ferrous metals, which minimizesthe amount of fuel consumed in the cupola in contact with the metalbeing melted. Another object is to provide a process of melting metals,and particularly non-ferrous metals, which is simple and economical topractice and which results in the production of a highly refinedmetal.

if not the entire, amount of heat necessary to melt the metals in thecupola is produced by burning,

externally of the cupola, fuel, such as pulverized or liquid pitch,pitch coke, petroleum coke, tar,

petroleum oil such as is used in oil-fired meta1-' lurgical furnaces, orgas, which fuels are substantially free of ash and materials having adeleterious effect upon the metal. Preferably, but not necessarily, anexcess of oxygen-containing gas, such as air, is employed to supportcom-' bustion of the fuel. The heating gases thus produced areintroduced and passedv through a bed',

In accordance with this invention, the major, I

such as pitch coke or petroleum coke, the use of such materialsminimizing the amount of slag formed and the amount of deleteriousimpurities taken up by the molten metal.

In cases where excess oxygen-containing gas is employed to supportcombustion of the fuel, the excess oxygen in the heating gases supportscom-' bustion of a portion of the coke bed, resulting in highertemperatures in the cupola than would be possible if such combustion didnot take place. The heating gases augmented by the products ofcombustion of the coke in the cupola then pass over the metal charge,heating the same to melting temperatures. The amount of oxygen'introduced into the cupola with the heating gases is controlled so thatcombustion of a relatively small proportion only of the charge of cokein' the cupola takes place and the gases leaving the charge of coke andcontacting with the metal contain little if any free oxygen. Hence, as aneutral or reducing atmosphere is maintained in the metal-containingzone of the cupola, excessive oxidation of the metal is avoided.

By producing the heating gases necessary to melt the metal externally ofthe cupola and passing the same through the charge in the cup0la. ascontrasted with prior practice involving the blowing of air underpressure through the charge, it is possible to avoid an excessiveoxidizing atmosphere in the cupola and so avoid metal lossesoccurringwhen an excessive oxidizing atmosphere is maintained in themetal-containing zone of the cupola to support combustion of coketherein. Furthermore, the use of fuels substantially free of ash,sulphur and other material deleterious to the metal, to produce theheating gases which are pas'sedthrough the metal, results in asubstanfurther insured by the employment of pitch or petroleum coke tosupport the charge of metal in the: cupola. Pitch and petroleum cokesare sumciently free of ash and other deleterious impurities so thatsubstantially no slag beyond that arising from impurities in the metalscharged is formed in the cupola; this simplifies the melting and re-"finirg process by minimizing opportunity for the production ofimpurities in and their introduction into the refined metal. Asherei'nabove indif tially pure refined metal since the combustiongases-do not introduce troublesome impurities into the metal. Thehighest quality of metal is undergoing practicing this invention withoutlimiting the.

claimed invention to such illustrative instance, Fig. 1 is a sideelevation, partly in section of such apparatus, and Fig. 2 is a planview of the apparatus of Fig. 1. r

Referring to the drawing, reference numeral l indicates a cupola furnacewhich may be of any well known type employed in the melting of metals.As shown in the drawing, the cupola may comprise a suitable cylindricalshell 2 lined with refractory material 3 surmounted by a stack 4 andhaving a charging inlet 5 situated in the upper part of the shell and atap opening 6 at the bottom. As needed, sand bed 1 may be disposed atthe base of the cupola with its face inclined downwardly toward the tapopening 6.

In accordance with this invention, gas distributing bustle pipe 8 isdisposed concentrically about the cupola, near the base portion thereof.The bustle pipe 8 communicates with the interior portion of the cupolaby means of conduits or tuyeres 9, four such conduits being shown inFig.

2. Conduit l connects the bustle pipe with combustion chamber ll linedwith refractory material l2. A fuel burner l3 extends through the rearwall M of the combustion chamber and communicates with a mixing chamberI provided with an air or other oxygen-containing gas inlet line l6 anda line I! for supplying liquid or gaseous fuel, such as liquid tar,pitch, petroleum oil, etc. The air entering It may be preheated bypassage in heat exchange relation with the combustion chamber oroherwisebefore introduction into the mixing chamber. In case it is desired toemploy solid fuel substantially free of sulphur and of other materialsdeleterious to. the metal being refined, such, for example, aspulverized pitch coke, a hopper l8 may be placed in communication withthe mixing chamber by means of a valve controlled line l9 substantiallyas shown. Coarse coke may be burned on grates in a Dutch oven, in ashaft furnace, etc. and the hot gaseous products of combustion free fromdeleterious impurities introduced into the cupola.

In the preferred operation of my invention a charge of cokesubstantially free of ash, sulphur and other materials deleterious tothe metal being refined, such as, for instance, petroleum coke or pitchcoke is placed on the sand bed. It is especially advantageous to employpitch coke made in a beehive oven such as described in theaforementioned Cushing' patent. The metalliferous charge which may beimpure copper, bronze or other metals is then placed upon the bed ofcoke. If liquid or gaseous fuel free of sulphur, ash and otherconstituents deleterious to the metal being refined is employed, as forexample, liquid tar, pitch, petroleum, or combustible gas, such fuel isadmitted into the mixing chamber l5 through line ll. Air or otheroxygen-containing gas introduced through line 16 mixes with the fuel,and the mixture passes to the burner I3 where it isignited by the hightemperature prevailing in the combustion chamber. Preferably, an excessamount of air isintroduced into the mixing chamber such that the gasesentering the coke charge contain from five to fifteen per cent. freeoxygen. This free oxygen supports combustion of a portion of the coke.In melting non-ferrous metals, e. 5.

bronze, by the process of the above mentioned Cushing patent, a ratio ofmetal melted to fuel consumed of from to 18 parts by weight of metal to1 part of fuel is ordinarily obtained, although under some conditions aratio as high as,20:1 may be reached. In accordance with the presentinvention the ratio of metal melted to bed fuel in the cupola consumedis greatly increased; for example, a ratio greater than 20:1 is usuallyobtained and this'ratio may even be 40:1 or higher depending oncombustion conditions in the burner and fuel bed as above described. Thewaste hot gas leaves through stack 4, and the molten metal is withdrawnthrough tap hole 6.

In cases where an excess of oxygen-containing gas is not employed tosupport combustion of the fuel burned externally of the cupola, air orother oxygen-containing gas may be introduced into the cupola in amountsufficient to support combustion of a portion of the pitch or other cokesupporting the metal charge.

If solid fuel is utilized to supply the heat necessary to melt thecharge, fuel reservoir I8 is supplied with pulverized pitch or otherfinely divided combustible material which is substantially free fromash, sulphur and other materials deleterious to the metal being refined.Air is admitted through inlet 16 at a pressure which may be of the orderof 2 to 5 pounds per square inch, into the mixer where it mixes with thesolid fuel. The resulting fuel mix passes to the combustion chamberthrough burner l3 where it islgnited and burns with the resultantformation of hot gases. The hot gases are led through the bustle pipe 8,through conduits 9 into the interior of the cupola, through the coke bedand into contact with the metallic charge, thereby melting it. Themolten metal trickles through the hot coke bed and is removed throughtap opening 6. Alternatively solid fuel may be burned on a grate or inother suitable apparatus outside the cupola, and the hotcombustion-gases introduced into the cupola through pipe l0. Since suchcombustion apparatus is well known, it is not illustrated in thedrawing.

-It will be noted that in accordance with this invention the cost ofmelting metal is substantially reduced as compared with the use of coke,particularly pitch coke, as the fuel, since only a portion of such cokeis consumed, the major portion of the heat being supplied by the burningof relatively low cost fuels externally of the cupola. Further, thetemperature in the melting zone can be accurately controlled whenoperating in accordance with this invention by regulation of combustionin the muffle furnace or combustion chamber II. If desired, the mufllefurnace lining may be built up from air-cooled bricks, the air passingthrough the bricks being introduced into the mixing chamber to supportcombustion of the fuel buried externally of the cupola or introduceddirectly into the cupola to support combustion of the pitch coke orother coke employed to support the metal charge. Melting conditions mayfurther be regulated by choice of fuels. Fuels giving highly luminousflames, e. g., tar, pitch, may be used to give high speed meltingwhereas fuels, such as natural gas, resulting in relatively non-luminousflames, may give relatively low speed melting.

While ,as hereinabove pointed out, the bed of fuel for supporting themolten metal within the cupola is preferably a bed of low-ash andlowsulphur coke, such as pitch or petroleum coke, in

- of ash and other materials having a deleterious effect upon thenon-ferrous metal within the many cases it is not necessary to use a bedof such high purity as pitch or petroleum coke, since in my process arelatively small ratio of coke to metal melted is consumed in thecupola.-

In fact, ordinary furnace or foundry coke (made from coal) will besatisfactory for some purposes. Practically allof the impurities takenup by molten metal in the process of the present invenditions, ordinaryfoundry coke may be of sumcient purity for use as thebed in the cupola.-

Since certain changes may be made in carrying out the above processwithout departing from the scope of the invention, it is intended thatall matter contained in the above descripton shall be interpretedasillustrative and not in a limiting sense. For example, while a bed ofpitch or petroleum coke has been disclosed as the support for the metalcharge, and such bed is preferred and should be employed to obtain allthe benefits of this invention, a bed of other coke (as above pointedout), such as ordinary coke, either high or low temperature coke,charcoal, or of refractory material capable of supporting the ourden,may be employed in lieu of pitch coke and the metal charge which may bebronze, lead, dross, copper, cast iron or steel heated by passing theproducts of combustion free of deleterious constituents thereover.

What is claimed is:

1. In the operation of a cupola furnace for the melting of non-ferrousmetal, those steps whichcomprise placing a bed of coke substantiallyfree cupola, placing-a charge of non-ferrous metal on said bed of coke,producing heating gases by the combustion of fuel substantially free ofash and other material having a deleterious effect upon said non-ferrousmetal, said heating gases containing a controlled excess of freeoxygen,-

passing said heating gases into said furnace and in controlled amountinto contact with said coke, the excess of free oxygentherein consuminga controlled minor portion only of said coke bed in metal from thecupola.

2. The method of refining non-ferrous metals in a cupola furnace inwhich the non-ferrous metal is supported on a charge of pitch cokesubstantially free of ash and material having a deleterious effect uponthe non-ferrous metal, which comprises producing, externally of thecupola, heating gases by the combustion of fuel substantially free ofash and of material having a deleterious eifect upon the non-ferrousmetal, utilizing a controlled excess of oxygen-containing gas to supportcombustion of said fuel, passing the heating gases through the pitchcoke and the nonferrous metal to be refined in the cupola, the excess offreeoxygen supporting combustion of the pitch coke within the cupola,the amount of free. oxygen in the'heating gases being controlled so thatonly a minor portion of the charge of pitch coke within the cupola isconsumed in the melting of the non-ferrous metal.

3. The method of refining non-ferrous metals in a cupola furnace inwhich the non-ferrous metal is supported on a charge of pitch cokesubstantially free of ash and of materials having a deleterious effectupon the non-ferrous metal, which comprises producif externally of thecupola heating gases by the combustion of liquid fuel substantially freeof ash and materials having a deleterious effect upon the non-ferrousmetal, utilizing a controlled excess of oxygencontaining gas to supportthe combustion of said fuel, passing the heating gases through the pitchcoke, the amount of free oxygen in the heating gases being controlled sothat only a controlled minor portion of the supporting charge of coke isconsumed, and passing the heating gases augmented by products ofcombustion of the pitch coke over the non-ferrous metal to melt thesame.

4. In the operation of a cupola furnace for the melting of non-ferrousmetal, those steps which comprise placing a charge of coke substantiallyfree of ash and other materials having a deleheating gases through saidcharge of non-ferrous metals to heat the metals to melting tempera-,tures, and withdrawing the molten metal from the cupola, the ratio ofmetal melted to coke consumed being greater than 20: 1.

' STUART PARMELEE MILLER.

